Lecture 4 Air Pollution: Particulates METR113/ENVS113 SPRING 2011 MARCH 15, 2011
Reading (Books on Course Reserve) Jacobson, Chapter 5, Chapter 8.1.9 Turco, Chapter 6.5, Chapter 9.4 Web links in following slides Web links in Assignment #2
Terminology Particulates An air pollutant that is not a gas Liquid or solid Aerosol Suspended particulate Small in size Droplet Liquid Relevant to air pollutant dissolved in water (acid rain, acid fog) Rain, cloud, fog, haze ( hydrometeors )
Characterization By size PM10 Amount (by mass) of particulate of diameter 10 μm PM2.5 Amount (by mass) of particulate of diameter 2.5 μm Regulatory (EPA, CARB, etc ) characterizations By chemical make-up (some important examples ) Sulfates Nitrates PAH (Polycyclic Aromatic Hydrocarbons) Soot ( Black Carbon, Elemental Carbon) Asbestos (an indoor pollutant, not so important in outdoor ambient air) Organic Carbon (includes PAH and others ) Inorganic (Sulfates, Nitrates, Metals, others ) By source Road dust, Sea spray Diesel particulate matter (regulated by CARB)
Timeline: Regulation of Criteria Pollutants CO SO 2 NO 2 Total Suspended Particles (TSP) Hydrocarbons (HC) PM10 PM10 PM2.5 Photochemical Oxidants Ozone (O 3 ) Lead (Pb) 1970 1976 1979 1983 1987 1997 current
PM10 & PM2.5 NAAQS and State Ambient Air Standards PM10 Total particulate mass less than 10 μm in diameter Respirable particulate Able to penetrate past nasal cavity into throat and lungs PM2.5 Total particulate mass less than 2.5 μm in diameter (a subset of PM10) Fine particulate Penetrates deep into lungs and may even penetrate into bloodstream Evidence increasingly building that PM2.5 is the main danger to human health (rather than PM10)
Ash, Combusted Plant Fiber, Elongated Ash, Soil Dust
Soot inclusion Soot Particles Coated Soot Particle Ammonia sulfate particles
Particle Size diameter actual particle idealized particle Note: Above pictures are 2-D, but real particles are 3-D
Annual Average PM10 and PM2.5 Concentration (not sure for what year, but recent ) PM10 (particles > 10 µm) PM2.5 (particles > 2.5 µm) Red circles indicate violations of national air quality standard (NAAQS): 50 µg m -3 for PM10 (no longer exists) 15 µg m -3 for PM2.5
Composition of PM2.5 (1) Sulfate Esther (1995-99) 4.6 ug m -3 Egbert (1994-99) 8.9 ug m -3 Abbotsford (1994-95) 7.8 ug m -3 Toronto (1997-99) 12.3 ug m -3 Nitrate Ammonium Black carbon Organic carbon Soil Other St. Andrews (1994-97) 5.3 ug m -3 Fresno (1988-89) 39.2 ug m -3 Quaker City OH (1999) 12.4 ug m -3 Kern Wildlife Refuge (1988-89) 23.3 ug m -3 Arendstville PA (1999) 10.4 ug m -3 Los Angeles (1995-96) 30.3 ug m -3 Mexico City - Netzahualcoyotl (1997) 55.4 ug m -3 Washington DC (1996-99) 14.5 ug m -3 Colorado Plateau (1996-99) 3.0 ug m -3 Mexico City - Pedregal (1997) 24.6 ug m -3 Yorkville (1999) 14.7 ug m -3 Atlanta (1999) 19.2 ug m -3
Composition of PM2.5 (2)
Composition of PM2.5 (3) From measurements (previous slides) six main categories make up PM2.5 composition in polluted air 1. Sulfates 2. Nitrates (includes ammonium nitrate, also called ammonium ) 3. Elemental Carbon ( black carbon, soot ) 4. Organic Carbon 5. Dust/Soil 6. Others (includes metals)
Secondary Aerosols (Sulfate, Nitrate & a portion of Organic Carbon) A secondary aerosol That is forms in the atmosphere from emitted precursor gases As opposed to primary aerosols (emitted directly from source) Precursor gases Sulfate: Precursor is sulfur dioxide (SO 2 ) Nitrate: Precursor is nitrogen oxides (NO x ) Ammonium Nitrate: NO x and Ammonia (NH 3 ) Secondary Organic Carbon: Volatile Organic Compounds (VOCs), Reactive Organic Gases (ROGs)
PM2.5 generally more of a problem in winter colder air, slower winds less dispersion of pollution colder temperatures favor nitrate and sulfate formation
PM2.5 generally more of a problem in winter colder air, slower winds less dispersion of pollution colder temperatures favor nitrate and sulfate formation
PM2.5 Emissions Direct Emissions (PM2.5 emitted from source, leads to primary PM2.5) Diesel Combustion (esp. trucks, construction equipment, ships, others ) Wood & Other Controlled Burning (Residential, Controlled Fires, Agricultural Burning) Road Dust Indirect Emissions (Emissions of Precursor Gases leading to secondary PM2.5) NO x : Combustion Sources (Cars, Trucks, Factories, etc ) SO 2 : Coal (outside CA); Shipping (in CA, Bunker Fuel heavy sulfur content) NH 4 (Ammonia): In CA Livestock! Organic Gases (VOCs, ROGs) Form secondary PM2.5 (sulfates, nitrates, secondary part of organic carbon) Some links http://www.epa.gov/oms/invntory/overview/pollutants/pm.htm http://www.epa.gov/air/emissions/pm.htm#pmnat Chapter 2 of http://www.arb.ca.gov/aqd/almanac/almanac.htm
Black Carbon Emissions (also called soot, elemental carbon) DIESEL, COAL DIESEL, COAL BIOMASS BURNING
Diesel Particulate Matter (DPM) A particularly dangerous portion of PM2.5 Comprised mostly of Soot ( elemental carbon ) Many different forms of organic carbon Sources: Diesel fueled engines (stationary and mobile) Heavy-duty trucks Construction equipment Others
WOW! Note: TAC = Toxic Air Contaminant, which is comprised of many air pollutants that are toxic http://www.arb.ca.gov/research/apr/reports/l3041.pdf
Some articles and websites (Diesel Particulate) http://www.ens-newswire.com/ens/feb2006/2006-02-22-03.html Summary of above article 1. Diesel particulates cause high cancer risk. 2. Risk is greater than other TACs combined (see also previous slide). 3. CARB diesel engine retrofit program for trucks and buses (http://www.arb.ca.gov/msprog/onrdiesel/onrdiesel.htm) http://www.arb.ca.gov/research/diesel/diesel-health.htm http://www.arb.ca.gov/research/diesel/diesel.htm http://www.arb.ca.gov/diesel/diesel.htm
Homework: Due Date: 4/7 (Day of Exam #3) Watch the following video http://video.google.com/videoplay?docid=3665914907157343039# (Alternatively, google Arden Pope video. You will then get a link to a google video (64 min) dated March 31, 2007 entitled Air Pollution and Health A Presentation from C. Arden Pope ) Answer the following (turn in 1-2 page summary on exam day): 1. Background: What is an epidemiological study and a cohort study? (You need to look this up on your own not in video.) 2. Summarize the epidemiological cohort studies presented by Dr. Pope in the video that link PM2.5 to adverse health effects. a) What were the specific studies? b) How were they designed. c) What were the findings (specific health effects) There will also be a multiple choice question about this 3. How did these studies affect development and other issues surrounding the PM2.5 NAAQS standards during the 1990s and early 2000s?
Meteorological Effects: PM2.5 Gravitational Settling & Deposition Visibility Reduction Regionally High PM2.5 concentrations (Inversion Layers, Wind Transport & Topography) See portions of Jacobson, Chapters 6 and 7 for reading support
Particle transport and sinks wind Particle emissions from some source Near source Large (> 10 um) and small ( 10 um) Large particles begin to fall to ground Important within first few hundred meters from source Far from source (II) Small particles ( 10 um) Little gravitational settling Removal through dry deposition Even farther from source (III) Small particles ( 10 um) Practically no gravitational settling Removal through dry deposition Air concentration reduced compared to II Source area Gravitational settling of large particles Dry deposition Dry deposition
Summary Large particles (> 10 um) o Removed very efficiently (i.e. near source) o Removed by gravitational settling Small particles ( 10 um) o Removed very slowly (very persistent in air) o PM2.5 especially persistent, since it is smaller o Removed through dry deposition
Air Pollution in Urban Area (Mexico City)
Air Pollution in Urban Area (Mexico City) Mixing Depth Polluted Air* Base of inversion layer * visibility reduction mostly due to PM2.5
Air Pollution in Urban Area (Los Angeles)
Particles and Visibility (Photos below generated by computer simulation) PM 2.5 = 7.6 µg/m 3 PM 2.5 = 21.7 µg/m 3 PM 2.5 = 65.3 µg/m 3
What is an inversion layer? Cool Air Below. Pollutants prevented from rising through inversion. Trapped below high concentrations.
Situation made worse by winds blowing inland and further trapping by topography
A Multiple Choice Exam Question Which of the following best characterizes direct PM2.5 emissions in California? a) Emissions of NOx from passenger car tailpipes b) Emissions of particulate from heavy-duty diesel powered trucks c) Emissions from dust lifted off the ground from road traffic d) Emissions of particulate from cargo ship traffic
Another Multiple Choice Exam Question An inversion layer is a layer in the atmosphere in which the air is. Inversion layers are important because. a) Warmer than the air below; they trap pollutants below the inversion thereby increasing concentrations b) Warmer that the air below; they speed up chemical reactions that form air pollution. c) Colder than the air below; they trap pollutants below the inversion thereby increasing concentrations d) Colder than the air below; they speed up chemical reactions that form air pollution.
Yet Another (!) Multiple Choice Exam Question Which gives a correct definition of secondary PM2.5? a) PM2.5 that is of relatively less concern in terms of health risk compared to primary PM2.5. b) PM2.5 for which there is only a secondary NAAQS or state ambient air standard. c) PM2.5 not emitted to the atmosphere, but is instead formed in the atmosphere from chemical reactions.